Abstract Poor cardiometabolic health, encompassing both cardiovascular and metabolic diseases, is the leading cause of preventable death worldwide. There is growing evidence that childhood exposure to stress increases lifespan cardiometabolic risk. The proposed study addresses 4 gaps in the literature recently identified by the American Heart Association: (1) the need for prospective studies, (2) the need to better specify periods of greater vulnerability to stress with regards to cardiometabolic health, (3) the need for more evidence on mechanistic pathways, and (4) the need for more studies that explore sex differences. Our central hypothesis that infancy is a important period for setting in motion processes that increase cardiometabolic disease risk. Our model of early life stress (ELS) will be orphanage-rearing experienced by children adopted internationally. We will assess cardiometabolic functioning in adolescence, the earliest age period when these assessments are associated with adult cardiovascular health. We will compare adolescents adopted as infants or very young children from orphanages into well-resourced homes with youth reared in their natal families of comparable educations and incomes. We will address three specific aims: 1) Determine the relationship between significant ELS in the first few years of life and cardiometabolic functioning in adolescence, 2) determine factors that mediate or partially mediate the association of ELS with cardiometabolic function and changes in functioning during adolescence, and 3) explore the sex differences in ELS- cardiometabolic risk associations. Under the first aim, arterial stiffness and fasting glucose, insulin, and lipids levels will be examined. For the second aim, the impact of ELS on cardiometabolic functioning in adolescence will be examined with the mediators of altered stress system activity, indices of immune aging, increased trunk fat mass and poorer health behaviors. In the third aim, sex differences will be examined in the outcomes in aim 1 and associations with potential mediators in aim 2. These aims are based on significant preliminary data. The impact of this study will be (1) improved understanding of the importance of the first few years of life for cardiometabolic health, (2) a deeper characterization of the mechanisms and pathways through which ELS-cardiometabolic risk is instantiated and (3) determination of whether there are sex differences in either the association or the pathways mediating cardiometabolic risk. These contributions are significant because they will demonstrate the need to begin interventions earlier in development and will identify novel treatment targets to mitigate future cardiometabolic risk and ultimately shift the odds for children experiencing ELS.